The present invention relates to a measuring system to detect dynamic quantities of a rotating body.
Dynamic quantities of a rotating body, particularly torques, have conventionally been measured by attaching a wire strain gauge to the rotating body and measuring a change in a resistance of a fine metal wire of the gauge. However, since a thin film easily develops a high cyclic fatigue, it is difficult for the wire strain gauge to maintain reliability for a long period when used in applications that cause high cyclic deformations, such as measuring strains and torques of rotating shafts. That is, the wire strain gauge has not been able to be used in applications that affect human lives and thus require very high reliability, such as automotive drive axels. Further, in forming a Wheatstone bridge for temperature correction four wire strain gauges need to be attached and their possible peeling and damage pose a problem of a degraded reliability. Also since a metal thin film is easily corroded, the wire strain gauges could not be used for a long period under corrosive environments or environments containing water.
Further, in measuring torques of a rotating body some provisions have conventionally been made, such as picking up a detected value of the wire strain gauges through wired slipping or preparing circuits including power supply, amplifier and transmission unit and transmitting the detected value wirelessly. This, however, tends to make the device complex, large and heavy. When it is attached to a shaft, the device can easily fall because of an increased centrifugal force acting on it. Since shafts easily deflect, various corrective measures, including re-establishing a balance, need to be taken. That is, although it is possible to take time and labor to perform test measurements using the wire strain gauges, they cannot safely be used for applications that require reliability. See JP-A-6-301881 for reference.
The present invention therefore provides rotating body dynamic quantity measuring system and device capable of restraining some of the problems described above.